The present invention relates to an optical pyrometer for optically measuring the temperature of molten metal such as steel, and more specifically to a less expensive and more accurate optical pyrometer.
It is generally difficult to receive radiant rays from molten metal such as steel because the molten steel is always covered with slag. This is the reason why it has been common to use immersion type thermocouples for measuring the temperature of molten steel.
An immersion type thermocouple is made of an alumel-chromel or a platinum-rhodium platinum thermocouple accommodated in a quartz cap at the end of a paper sleeve. Such an immersion type thermocouple can be used only once or twice and is an article of consumption which cannot be used repeatedly.
Such immersion type thermocouples, especially the platinum based thermocouples, are very expensive. However, temperature measurement of molten steel is essential to providing quality control of steel products, thereby requiring considerable expenditures for providing such temperature measurement of molten steel.